Modelling of microwave elliptical and conical tip sensors for in vivo dielectric measurements

This paper describes the modelling of two simple, fast and accurate microwave elliptical and conical tip sensors for in vivo dielectric measurements. Modification of the existing model for easier and accurate dielectric measurements was carried out. An intensive comparison between elliptical, conical tip and open ended sensor for dielectric measurements were conducted. The sensors with different sizes built using commercial RG 402 and RG 405 coaxial cable were developed and tested at frequencies 0 GHz to 8 GHz. MATLAB algorithms were developed for dielectric calculation using capacitance model, admittance model, virtual line model, and modified capacitance model. It was found that the modified model proved to be accurate when compared to Cole-Cole model for several known liquids. A set of agriculture in vivo preliminary experiment was then carried out with three types of sample namely apple, mango and potato. The performances of the elliptical and conical tip sensors for in vivo dielectric measurement were compared to open ended coaxial. The modified models were found to be competitive and more practical in term of accuracy and measurement time for in vivo dielectric measurements.